The invention relates to a semiconductor base device with a wiring substrate and an intermediate wiring board for a semiconductor device stack, and to a method for its production. In particular, the invention relates to a wiring substrate and an intermediate wiring board between which a semiconductor chip is arranged.
In the case of conventional semiconductor devices with a wiring substrate, external contacts are arranged on the underside of the wiring substrate and at least one semiconductor chip, for example a computing element such as a DSP (digital signal processor) or such as a memory device (a DRAM), is arranged on the upper side of the wiring substrate, in the center of the wiring substrate.
If a conventional device of this type is to be used as a stackable semiconductor device for a semiconductor module having stacked semiconductor devices, only the edge regions of the wiring substrate can be available for the attachment of external contacts of a stacked semiconductor device, since the center of the wiring substrate is taken up by the semiconductor chip itself. The number and arrangement of external contacts of the semiconductor device to be stacked is very restricted as a result, so that many known types of package, such as BGA (Ball Grid Array), FBGA (Fine Pitch Ball Grid Array) or LBGA (Large Ball Grid Array) packages, cannot be stacked on a conventional semiconductor device with a wiring substrate, since the solder balls acting as external contacts are arranged such that they are distributed over the entire underside of semiconductor devices of this type.
A solution to this stacking problem is known from the document DE 101 38 278. For stacking, conventional semiconductor devices with a BGA, FBGA or LBGA package are provided with additional flexible wiring films that have a larger surface area than the semiconductor devices to be stacked and protrude beyond the edge of the semiconductor devices, so that they can be bent in the direction of a semiconductor device of a semiconductor device stack that is arranged thereunder or thereabove and can be electrically connected to the semiconductor device arranged thereunder or thereabove by way of the flexible film.
A semiconductor module with semiconductor devices stacked in such a manner has the disadvantage that the semiconductor devices cannot be stacked with the lowest possible space requirement, especially since the bent-over wiring film also requires a minimum bending radius which cannot be any less without the risk of microcracks in the wiring lines arranged on the wiring film. Forming a wiring film from a suitable highly flexible film and leading it from the underside of a semiconductor device over one of the edge sides of the semiconductor device onto the upper side of the semiconductor device, so that external contact areas of the wiring film can be arranged in any distributed manner and connected to one another both on the underside of the semiconductor device and on the upper side of the semiconductor device, is extremely complex and requires cost-intensive production methods.
A semiconductor base device structured in this way additionally has the disadvantage that line paths that are relatively long and also vary in length exist over the film between the semiconductor chip in the lower semiconductor base device package and the stacked semiconductor device arranged on the semiconductor base device, so that in communication applications delay differences and crosstalk in the coupling of radio-frequency signals may occur.
A further variant for stacking semiconductor devices one on top of the other is the possibility of using interposers which have on their upper sides external contact areas that can be arranged in any distributed manner over the entire surface, their size and arrangement corresponding to the size and arrangement of external contacts of a semiconductor device to be stacked. Arranged on the underside of the interposer or of an intermediate connecting part are solder-ball-based 3D contacts, which are of such a large diameter as to allow bridging of the interspace between the interposer and a wiring substrate of a semiconductor device arranged thereunder, with a mounted semiconductor chip, and permit the connection by way of these large-volume 3D contacts between the interposer and the wiring substrate of the semiconductor device arranged thereunder in edge regions of the wiring substrate.
For this purpose, these 3D contacts have a diameter that is greater than the thickness of the semiconductor chip of the semiconductor device arranged thereunder, which has the disadvantage that such 3D contacts of the interposer cannot be arranged as close together as desired on edge regions of the wiring substrate or of the interposer, and consequently have to be disadvantageously arranged with a widely spaced connection pattern. Consequently, an extensive, relatively high pitch has to be provided for an arrangement of such 3D contacts, in order that they do not touch one another. For a semiconductor base package having a wiring substrate and an interposer with 3D contacts, this results in a disadvantageously enlarged base package if an adequate number of electrical connections between the interposer and the wiring substrate are to be ensured in the edge region of the same.
For these and other reasons, there is a need for the present invention.